Healthy weight

Obesity professor explains 5 reasons why calories don't count and what to focus on instead | Professor Giles Yeo

9th Sep 2026

Next time you look at the calories on the back of a packet or the nutritional breakdown of a recipe, remember that number doesn't tell you the whole story.

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It says nothing about the nutrients, the quality of the food, how satisfying it'll be, or even how many calories your body will actually absorb.

To unpack it all, I'm joined by Professor Giles Yeo, Professor of Molecular Neuroendocrinology at the University of Cambridge, MBE, and author of the brilliant book Why Calories Don't Count.

We cover:

5 reasons calorie counting matters less than we think
Why "low-cal" doesn't always mean healthy
Why we don't absorb every calorie we eat
Why the calories in nuts, avocados and seeds aren't the same as the calories in a ultra-processed foods, even when the numbers match
Is fruit juice really healthy?
3 strategies to maintain a healthy weight

I hope this changes the way you think about calories and gives you a few practical ideas you can start using straight away.

If you know someone who's always checking the calorie label before anything else, send this episode their way.

As always, thanks for listening!

Dr Rupy x

Episode guests

Professor Giles Yeo

Giles Yeo is an alumnus of Wolfson College and got his PhD in molecular genetics from the University of Cambridge in 1998, after which he joined the lab of Prof Sir Stephen O’Rahilly, working on the genetics of severe human obesity. Giles Yeo is now a Professor of Molecular Neuroendocrinology and programme leader at the MRC Metabolic Diseases Unit in Cambridge, and his research currently focuses on the influence of genes on feeding behaviour & body-weight. In addition, he is a fellow of Wolfson College and Honorary President of the British Dietetic Association. Giles is also a broadcaster and author, presenting science documentaries for the BBC, and hosts a podcast called ‘Dr Giles Yeo Chews The Fat’. His first book, ‘Gene Eating’ was published in December 2018, and his second book, Why Calories Don’t Count’ came out in June 2021. Giles was appointed an MBE in the Queen’s 2020 birthday honours for services to ‘Research, Communication and Engagement’. He won the Society for Endocrinology Medal in 2022.

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Obesity professor explains 5 reasons why calories don't count and what to focus on instead | Professor Giles Yeo

Episode guests

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